District of Columbia Deputy Mayor Alphonse Hill resigned amid allegations that he accepted kickbacks, the latest in a series of problems for officials of Mayor Marion Barry's Administration. It was disclosed last week that Hill had accepted $3,000 in payments from an auditing contractor who heads a firm that has received hundreds of thousands of dollars in city business. A federal grand jury is investigating. Hill's resignation is effective at the end of the month. Barry had no comment on the resignation. The deputy mayor said he was not forced out by Barry but quit to ensure the integrity of the city's financial system, which he helped design.